Track Testing - How To Go Testing

1/12We get better through track testing. A plan is developed and data is collected accurately in order to properly analyze what went on and what changes made the most impact, both positive and negative. That is how we learn.

Track testing provides an opportunity to dial in the car to a particular track for speed and consistency. Most events don't offer enough time for adequate evaluation of our chosen setups, so we need to take advantage of every chance we get to go testing.

I recently tested at several racetracks with an ASA Late Model Series South race team and recalled some of my previous experience over the years. What I learned was that the basics don't change, even with some of the new and innovative setups we now see. Suspension binding and broken shocks still throw off test results.

There is a specific order we must follow during testing to get the most out of the experience. Let's look at how we might organize and run a typical test session and discuss methods and procedures we can use for a more productive session. The process is mostly the same for dirt and asphalt, with some minor differences.

All testing and practice involves trying different combinations of setup and chassis geometry that might make the car faster. As we have stated before, we are searching for an unknown by making intelligent choices in reasonable directions. What we don't want to do is start out with a car we don't know very well and throw springs and other parts at it while hoping for a miracle. The top race car consultants would never work with a car that didn't have critical information readily available.

2/12The monoball upper ball joint affords easy changes to the upper control arm angles to reposition the moment center. We must make sure that there is no binding in the suspension. There should be a spacer between the stud nut and the monoball.

The overall goal of testing is to find a setup combination that is initially fast and remains fast for a long time. It should be good on the tires, comfortable for the driver, and should enable the driver to outrun the competition from start to finish.

On asphalt, the final setup is probably the one we will qualify and race with, given small changes between the two. For dirt, the changes required for each segment might be much different. That does not mean we cannot test on a track that is consistent.

Dirt testing involves trying various settings and bolt-on parts to find what makes the car do what we need it to do. Getting the car to turn better will help us throughout an event, and finding methods of adding forward bite can help us get off the corners better for the dry and slick conditions.

A primary goal might be to learn the process of making changes to meet track conditions. There is an order and logic to adapting to changing track surface grip levels. Becoming comfortable with making those changes can be a huge performance gain.

3/12Dirt Late Model chassis have many components to adjust. This car has a lift arm that can be tuned for acceleration and deceleration and a four-bar rear suspension with multiple holes for rear steer tuning. This provides lots of possibilities for a team to try when testing.

It is most important to be familiar with the car prior to going to the racetrack for practice or testing. This means that the front and rear geometry have already been evaluated, the car is aligned, and a dynamic analysis of the spring combinations has been accomplished to balance the two suspension systems. Also, the shocks have been dyno'd and tested, the springs have been rated, the steering system has been checked for Ackermann, the car has been weighed, and the motor has been prepped.

The type of racetrack should be taken into consideration if this is the first time the team has been there. If it has a different banking angle from what the team is used to, a different moment center design might be in order. High-banked tracks have little need for traction-enhancing technology, so rear steer characteristics and ride height must be planned if excess chassis travel is an issue. If the track is flatter, methods of creating bite off the corners should be included in the planning.

If the team is unaccustomed to the length of the track, a rear gear in an acceptable range should be calculated or someone on a team that has run on the track should be asked about gear ratio. If testing is taking place on dirt, the correct tires are needed for the anticipated conditions.

In the days before we leave the shop, we must prepare a plan of attack that defines the changes we will make and the areas in which they are made. This plan may be written on paper or mentally noted. It should be discussed with the entire crew so they can have input into the process and know the direction the test will go in order to be prepared in their particular areas of expertise.

4/12A different setup is mounted on shocks at the shop before leaving for a test. That way, the wheel weights are accurate and the new setup can be installed quickly for a back-to-back run to see if it is faster.

Having a prepared plan is very important for getting good results. As the test proceeds, the result of each change (both positive and negative) should be noted. We probably learn more from the negative results than from the ones in which gains are made. That is because we more readily remember losses in lap times and how to avoid the things that the car does not like.

If different combinations of spring rates are to be used, we need to weigh the car with each combination of springs and note the position of the spring adjusters, which may be the coilover rings on the shocks or the jack screws used in the big spring cars. Doing this allows us to quickly make spring changes at the track and ensure that the weight distribution has not changed.

If we intend to compare different layouts of shocks when making individual corner changes, we need to mark the shocks according to where they will be placed on the car and give them set numbers. The tire sets must be marked as well so that we do not mix tires among sets. Using a tire of a different age (meaning date or laps used) from the other three can throw o the setup quite a bit. Many tests have been upset by the use of an odd tire.

Once we have arrived at the track and unloaded the car, we need to establish a pitting position for the car that is relatively level. We should have easy access to the tool cart, the trailer, and other track facilities that may be needed. The spots around the tires are marked with duct tape in order to park the car in the same position after each run.

Many teams weigh the car in that location and note the relative weight distribution if the scales cannot be leveled. The weights read will almost always vary from the shop numbers due to the scales being out of level.

It is best to level the scales and weigh the car before testing. Then, after all the testing is done, the car is reweighed to see how the weight distribution might have changed from the various adjustments.

5/12Recording turn segment times allows direct comparison of your times to those of your competitors. Turn segment evaluation does a better job of telling us when we are correctly set up than the evaluation of lap times that include straightaway acceleration.

Once we hit the track, we need to be able to measure our on-track performance. There are two components of speed: the motor/drivetrain combination that gets us down the straightaways, and the chassis setup combination that gets us through the turns. Since we work on these separately, we need to measure them separately.

A car can be the fastest one in the turns but not up to par down the straights for a number of reasons. If we have lap times that include turn segment times, we can compare our times to that of our competition. Turn segment times tell us all we need to know about chassis setup experimentation.

We should always take turn segment times in addition to total lap times and compare both with other fast cars. Remember, if we can improve the midturn speeds, we can also improve the straightaway speeds. It is generally accepted that speed gained in the turns is carried all the way around the racetrack.

If we use previously run tires, the age of the tires must be taken into consideration when making comparisons to other cars. If we start on stickers and then run 50 laps of testing, we can expect to lose time to the tires. If our lap times stay consistent, then the changes we are making are probably enhancing our performance. Eventually switching to newer tires will show the positive results of our changes.

It is not a good idea to chase a competitor who has newer tires than ours. If we struggle to make adjustments in an attempt to make up the three- or four-tenths difference, we could put our setup out in left field, never to return.

Some teams use unsupervised tests as a chance to "cheat up" the car to go fast. If an opposing team is too fast, we should not try to keep up by making wholesale changes. Once that team returns to regular competition, where the rules must be observed, the times will return to normal.

6/12Testing also includes driver orientation to a new and different racetrack. Here, we see a strange configuration for a track that has a smaller radius in Turns 1 and 4 and a larger radius in Turns 2 and 3. This arrangement will take some getting used to, as the driver must learn to accelerate sooner in 1 and 2 and brake less and later going into 3 and 4.

The driver should initially make several slow five-lap circuits and then five faster circuit runs to shake down the car. This establishes that the brakes work as expected, the wheels are on tight, the air will stay in the tires, and there are no water or oil leaks. The transmission and rearend lubricants will also be brought up to temperature. Two more five-lap runs must be made following the initial outing in order to get meaningful tire temperatures.

After each of these runs, we record the tire pressures and/or temperatures, tire sizes, engine water and oil temperatures, and the number of laps run in each session. Then, we make hard copy records of the data in addition to digital records (stored in the tire temperature/pressure box or on a computer). It is fine to have digital records, but we all know how easy it is to lose digital information. Doing both is the best way.

Once the driver is confident that the car is sound, longer and faster runs can be done. In the next series of runs, the driver needs to stay out at least 10 laps so that the tire temperatures will be sufficient to show how the tires are working. Unless the car has a serious handling problem, this should not be an issue. The car should be viewed from a high vantage point. We should pay attention to how the car looks, where the driver's hands are positioned, and how far the wheels are turned while in the middle of the turns.

7/12The crew must communicate the changes and the reasons for those changes to the driver. That way he or she can know what to expect the next time out on the racetrack. Feedback from the driver to the crew is essential in order to properly evaluate the setup.

The next step involves evaluating the tire temperatures, pressures, and overall handling balance. Quick adjustments are made to the front tire cambers and all four tire pressures if the temperatures dictate doing so. The handling cannot be properly evaluated if these issues are not resolved right away. No chassis adjustments will be made until we have taken care of the tire issues.

Excess steering input at midturn, inability to keep the car low in the turns, and a car that snaps loose off the turns are all indications of a tight setup. The driver should run the turns at a speed lower than normal and note the position of his or her hands. Once the car is up to speed, the driver should again note hand position. If the steering is significantly different, the car is either tight or loose.

We should record driver and crew comments regarding handling and engine performance. If the car is not neutral, we will make changes to improve the handling while working to maintain a balanced setup.

There is a difference between handling balance and dynamic balance. The car is neutral when it is neither tight nor loose. We can easily adjust most cars to make them neutral. This may make the car faster, but it is not our primary goal. The car needs to be neutral in handling, and the front and rear suspension must be in sync. When both ends of the car are working together, we will truly have a balanced car that is fast and consistent.

8/12Significant tire information is written on the sidewall of the tire so that it is easily apparent. This tire is from the right front and is from set three. It has been used at Lonesome Pine Raceway and was first run on June 29.

We must always evaluate and correct the midturn performance first. Balancing the car at this steady state point on the track will also help balance it on entry and exit. Steady state is defined as a condition in which the car is neither accelerating nor decelerating. So the dynamic effects of longitudinal weight transfer from braking or motoring off the corner are not affecting our evaluation at this point in the test.

We can interpret the balance of the car by evaluating the tire temperatures. The easiest way to make a car neutral is to adjust the crossweight. Crossweight is the percentage of the total weight of the car that is supported by the right-front (RR) and left-rear (LR) tires as read on the scales. Lowering the RF and LR corners while raising the LF and RR corners reduces crossweight and loosens the car. All four corners must be adjusted to cause a change in crossweight.

After we have made the car neutral in handling, we need to make a couple of hard runs and note the tire temperatures. The dynamics of the front and rear suspensions working with or against each other will show in the tire temperatures. The LF tire will be near the same temperature and working as hard as the LR tire in a balanced setup.

If the LF tire is the coolest tire on the car (by far the most common condition), then changes should be made to the setup to help heat that tire up by making it work harder. With the popular big bar and soft spring (BBSS) setups, the opposite is usually true. The LR tire might be the coolest tire on the car, and we need to make changes to cause the left-side tires to be the same.

Tire wear can tell us a similar story when racing on dirt. Dirt teams rarely take tire temperatures. They feel the tires for temperature, so it must be somewhat important. But tire wear can also tell us how hard a tire is working.

9/12It is very important to observe how the car looks and the line the driver is driving around the track. We can detect setup problems and arrive at solutions when a trained observer is watching.

Here are a few changes that help us move toward a more balanced state.

To reduce the tendency for the rear to outroll the front:

1. Increase the RR spring rate or reduce the rear spring split if the RR is softer.2. Raise the Panhard bar.3. Soften the RF spring rate (only on lower-banked tracks).4. Stiffen the LF spring rate.5. Move the moment center to the left.

To reduce the tendency for the front to outroll the rear (as is often the case when teams try the BBSS setups):

The crossweight should be adjusted with each change in order to maintain the neutral handling. The crossweight has to increase in the first examples because the car turns better as the LF tire begins to have more grip and work harder. We need to tighten it using a higher percentage of crossweight.

In the second set of examples, where the front outrolls the rear, the crossweight needs to be reduced as the rear tires develop more grip.

10/12The upper mounts on this pavement Late Model are slotted to allow quick camber adjustments. The tire temperatures must be evaluated first to see if the heat is distributed properly across the face of the tire. Quick changes to tire pressures and cambers will correct any problems.

If Ackermann has always been used by the team to help the car turn in conjunction with a tight and unbalanced setup (the LF tire runs cooler than the LR tire), then the Ackermann has to be reduced and/or eliminated as changes are made to load the LF tire. A tire that is not working much (less vertical load on it) gains traction by using Ackermann. If we load that tire, it will really take off in the steered direction and work against the RF tire. The end result will be a severe push as the two front tires try to go in different directions, ultimately giving up their grip on the track.

Finding the dynamic balance for the car is not the end of our goal. Rather, it is the very foundation of a good setup. It is the first and most important step in getting ready to race. Small changes to the setup can be felt by the driver as never before, and the setup can be further fine-tuned for improved entry and exit performance.

Entry problems are almost always caused by rear alignment issues or incorrect shock rates (mostly in the RF and LR corners of the car). The rear end must be aligned properly and square to the centerline of the car. Failure to do so results in a long and hard struggle to overcome a poorly aligned rear end ultimately to no avail. No setup change can effectively overcome an alignment problem.

If we decide to tune entry performance with shocks, we will work with compression rates in the RF and rebound rates in the LR. A RF shock that is too stiff on compression might cause a push on entry. If the RF shock is far too soft on compression, it may also develop a push due to sudden and excessive suspension movement. The result is excess camber change that causes the RF tire to lose grip.

Excess LR shock rebound may cause the car to be loose on entry as the weight is transferred to the front while braking. The LR shock should allow the LR tire to move in rebound to help it maintain contact with the racing surface as the car pitches forward and to the right on entry.

11/12Changing springs to affect the handling of the car is made more accurate by the use of an individual wheel scale (the one shown is manufactured by Intercomp). The wheel is weighed with the old spring and then the new one is installed. The spring height is adjusted so that the wheel weight remains the same.

Spring split has an effect on entry performance, too. At flatter tracks, a stiffer LF spring over the RF spring helps entry stability in most cases. To the driver, a stiffer RR spring over the LR spring might feel like the rear end is not under the car and may prevent him or her from going into the corner deep enough on the banked tracks. Spring changes also affect the dynamic balance of the car, and we need to re-evaluate the tire temperatures and make changes to the Panhard bar to rebalance the setup after a spring change.

Problems associated with corner exit involve either a tight-off or loose-off condition. If we introduce methods to gain bite off the corner, we might end up with a car that does not turn. The changes we make to improve exit performance should not change the midturn balance. Changes to spring rates, spring split, Panhard bar height, and crossweight will affect and probably ruin midturn balance. So, how do we tune exit performance?

The tracks where we usually see exit issues are mostly the flatter tracks with associated lack of grip. The combination of lateral forces that come from turning the car and the torque associated with power application tend to overload the grip capability of the rear tires. So we need to develop ways to increase the amount of grip the rear tires have available on exit off the corners while not affecting the established midturn balance.

We can experiment with various designs of pull bars, pushrods, lift arms, and associated rear steer that happens only on acceleration. The goal is to reduce the shock to the rear tires upon initial application of power and increase the total rear grip level by introducing rear steer (to the left) to the rear geometry. The more the rear tires are steered, the more traction they will have, just as we have learned about the front tires associated with steering input.

There is a limit to how much rear steer we can use before the car becomes too tight on exit. Larger amounts are more tolerable on dirt than on asphalt. A few ten-thousandths of an inch of wheel movement fore and aft can be felt by the driver on asphalt, whereas an inch or more of wheel movement is not unheard of on dirt.

12/12

Sticker tires should be saved for the last runs of the day after the car is dialed in. If the setup is good, we can make a qualifying run on fresh tires. After that run, a 25- or 30-lap run is made using the newer tires to see if the lap times stay consistent. A truly balanced setup will provide lap times that fall off less than the competition's as more laps are run on a single set of tires.

Back at the shop, we review our notes and learn from the gains and losses. All of the results are valuable. The more we learn about the effects of changes, the better we become at making quick adjustments during a racing event. The top teams make a point of knowing how each chassis adjustment affects all of the other parameters involved with their setups.

Incorrect tire stagger, bent shocks, and suspension binding are some of the peculiarities that can ruin a test session. If radical setup changes do not seem to affect the expected result, then a mechanical problem must be sought and fixed. Stagger almost always closes; it doesn't open. Given the choice, we should use a slightly larger stagger than what we may need.

Test notes should be kept available for review. Testing should take place as often as we can afford and whenever the track is available. If goals are set, performance will improve and racing will be that much more enjoyable. Let us know how you do by sending an e-mail to bob.bolles@primedia.com. We promise not to share your secrets. Good luck.